There's no official API for Kbin yet. The fact that there are any apps being worked on for Kbin at all yet is a miracle. I would have prioritized an API as a very urgent feature in order to let app developers get some good apps out as soon as possible, to take advantage of the initial Reddit migration hype. Lemmy has a big advantage over Kbin because of all the apps that are coming out right now. Not that it's a competition, of course. Kbin has around 50.000 users already, as far as I know. And the Kbin devs have a lot on their plates already, some of which is critical to allow the site to work well for this number of users.

So, it's easy for me to sit here and say what I think they should have prioritized differently. I don't have all the inside information, so take my opinion with a grain of salt. I'm really happy that Kbin is doing as well as it is now. @ernest has been working tirelessly, and I hope it becomes something he can live off of too, somehow.